Rechargeable lithium battery and process for the production thereof

ABSTRACT

A thin rechargeable lithium battery having a battery main body enclosed between sealing members (a) and (b), at least sealing member (a) having a concave portion that extends to either side from a central position so as to have a peripheral collar portion (a-i) which surrounds the concave portion, sealing member (b) having a peripheral collar portion (b-i) corresponding to the collar portion (a-i) of sealing member (a) and the two sealing members (a) and (b) being opposingly arranged such that the face of said concave portion of sealing member (a) faces sealing member (b) through the battery main body, wherein collar portions (a-i) and (b-i) are mutually welded, and either sealing member (a) or (b) is provided with a power output terminal having electrical continuity with the battery main body and an insulating portion for insulating said terminal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rechargeable lithium batterypreferably shaped in a thin form and a process for producing saidrechargeable lithium battery.

2. Related Background Art

In recent years, the global warming of the earth because of theso-called greenhouse effect due to an increase in the content of CO₂ gasin the air has been predicted. For instance, in thermal electric powerplants, thermal energy obtained by burning a fossil fuel is beingconverted into electric energy, and along with burning of such fossilfuel, a large amount of CO₂ gas is being exhausted in the air.Accordingly, in order to suppress this situation, there is a tendency ofprohibiting to newly establish a thermal electric power plant. Underthese circumstances, so-called load leveling practice has been proposedin order to effectively utilize electric powers generated by powergenerators in thermal electric power plants or the like, wherein asurplus power unused in the night is stored in rechargeable batteriesinstalled at general houses and the power thus stored is used in thedaytime when the demand for power is increased, whereby the powerconsumption is leveled.

Now, for electric vehicles which do not exhaust any air pollutingsubstances such as CO₂, NO_(x), hydrocarbons and the like, there is anincreased demand for developing a high performance rechargeable batterywith a high energy density which can be effectively used therein.Besides, there is also an increased demand for developing a miniature,lightweight, high performance rechargeable battery usable as a powersource for portable instruments such as small personal computers, wordprocessors, video cameras, and cellular phones.

Under such circumstances, there have been proposed a nickel-metalhydriderechargeable battery and a rechargeable lithium battery which willcomply with such demand. And various researches and developments havebeen made in order to more improve their performances.

For the nickel-metalhydride rechargeable battery, although it isinferior to the rechargeable lithium battery in terms of beingrelatively heavier, it has advantages in that it can be relativelyeasily produced at a reduced production cost in comparison with therechargeable lithium battery. In view of this, nickel-metalhydriderechargeable batteries have been often using as power sources ofportable instruments. Besides, nickel-metalhydride rechargeablebatteries have started using as power sources of certain electricvehicles.

For the rechargeable lithium battery, there have been proposed variousrechargeable lithium batteries having an anode comprising a given anodeactive material such as a lithium metal, a lithium alloy, a carbonousmaterial, or the like and having a cathode comprising a given cathodeactive material such as manganese dioxide, lithium-cobalt oxide,lithium-nickel oxide, or the like. These rechargeable lithium batterieshave been evaluated as being superior to the nickel-metalhydriderechargeable battery particularly in a viewpoint that they are expectedto have a relatively higher energy density. And researches anddevelopments have been made of these rechargeable lithium batteries inorder to put to practical use. Some of them have been practically usingas power sources of particularly portable instruments.

Incidentally, for the configuration of such rechargeable battery used ina portable instrument, a cylindrical shape or a prismatic shape isadopted in many cases. In the case of a prismatic rechargeable battery,it can be designed to be thinner than a cylindrical rechargeablebattery. Thin-shaped prismatic rechargeable batteries have been oftenusing in compact portable instruments.

Now, a cylindrical rechargeable battery is generally prepared in thefollowing manner. A separator is sandwiched between an anode and acathode such that the separator is partly protruded at each end side,followed by spirally winding about a given axis so as to form acylindrical body comprising the separator/the cathode/the separator/theanode/the separator. The cylindrical body is inserted in a cylindricalbattery vessel through its opening. A necking is formed in the vicinityof the opening of the battery vessel. Then, an electrolyte solution isintroduced into the battery vessel so that the separator is impregnatedwith the electrolyte solution. Thereafter, a capping capable of servingalso as an external terminal and which is provided with an internalpressure release vent, a PTC (positive temperature coefficient device),and a current-shutoff device is put on the necked portion of the batteryvessel so as to cover the opening, followed by being caulked through apacking. By this, there is obtained a cylindrical rechargeable battery.

A prismatic rechargeable battery is generally prepared, for instance, inthe following manner. A separator is sandwiched between an anode and acathode, followed by winding about a given axis to form a cylindricalbody comprising the separator/the cathode/the separator/the anode/theseparator. The cylindrical body is shaped into a flat body by means ofpressure forming. The flat body is inserted in a prismatic batteryvessel through its opening. Then, a capping capable of serving also asan external terminal and which is provided with an internal pressurerelease vent, a PTC (positive temperature coefficient device), acurrent-shutoff device, and a liquid introduction port is put on theopening of the prismatic battery vessel, followed by subjecting to laserbeam welding to seal the inside of the prismatic battery vessel.Thereafter, an electrolyte solution is introduced into the prismaticbattery vessel through the liquid introduction port provided at thecapping so that the separator is impregnated with the electrolytesolution. Then, the liquid introduction port is sealed. By this, thereis obtained a prismatic rechargeable battery.

Any of the cylindrical battery vessel used in the preparation of thecylindrical rechargeable battery and the prismatic battery vessel usedin the preparation of the prismatic rechargeable battery is formed bydeep-drawing an appropriate metallic member such as a nickel-plated ironplate, an aluminum plate, or a stainless steel plate.

Particularly in the above method of preparing a prismatic rechargeablebattery, it is required to use a relevant prismatic battery vessel, andsuch prismatic battery vessel is formed by deep-drawing an appropriatemetallic member such as a nickel-plated iron plate, an aluminum plate,or a stainless steel plate. In this case, there is a limit for themetallic member which can be processed to form such prismatic batteryvessel by way of deep-drawing. Specifically, in the case of using ametallic member such as a nickel-plated iron plate, an aluminum plate,or a stainless steel plate, a prismatic battery vessel formed by way ofdeep-drawing unavoidably becomes to have a relatively large thickness ofabout 5 mm or more. This situation is similar also in the case offorming a cylindrical battery vessel by way of deep-drawing.

In order to form a prismatic battery vessel having a thickness which isthinner than aforesaid thickness, it is considered to adopt a method offirst forming a prismatic battery vessel by way of deep-drawing andgrinding the walls of the prismatic battery vessel in the thicknessdirection. However, this method results in a remarkable increase in theproduction cost of a prismatic rechargeable battery and therefore, it isnot acceptable in practice.

Separately, when the battery vessel in any case is of a thin thickness,the capping is necessary to have a thin thickness accordingly. When thecapping is of a thin thickness of, for instance, less than about 5 mm,it is extremely difficult to work a terminal cap and an insulating moldat the capping and it is also extremely difficult to work a liquidintroduction port at the capping. In addition, the battery vessel andthe capping are welded by means of laser beam welding in many cases. Thewelding in this case exerts a thermal adverse effect to the insulatingmold situated in the vicinity of the position where the welding isconducted.

Incidentally, in recent years, there has been developed a so-calledsheet type rechargeable battery capable of being thinned, comprising abattery main body covered by a laminate film, wherein said battery mainbody comprises an ion conductor disposed between an anode and a cathode,said ion conductor comprising a separator impregnated with anelectrolyte solution, a gelated electrolyte or a solid electrolyte.However, this sheet type rechargeable battery has disadvantages suchthat because the laminate film is insufficient in terms of the physicalstrength, the battery is liable to deform or it is liable to be damaged,and therefore, there is a limit for a range where the battery can beused.

FIGS. 10(a) and 10(b) are schematic views illustrating a rechargeablelithium battery having an armor comprising a laminate film, as anexample of aforesaid sheet type rechargeable battery.

Particularly, FIG. 10(a) is a schematic perspective view of saidrechargeable lithium battery when viewed from the lateral direction, andFIG. 10(b) is a schematic cross-sectional view of a peripheral portionof said rechargeable lithium battery, taken along the line D-D, and whenviewed from above.

In FIG. 10(a), reference numeral 1001 indicates a pair of power outputterminals extending from a battery main body 1003 installed in a packformed using a laminate film 1005. The battery main body 1003 comprisesan ion conductor disposed between an anode and a cathode.

As will be understood with reference to FIG. 10(b), the laminate film1005 comprises an aluminum foil 1007 (having a thickness of, forinstance, about 10 μm) sandwiched between a pair of plastic films 1006(having a thickness of, for instance, about 10 μm) which are insolublein solvents. The aluminum foil 1007 serves to prevent moisture frominvading into the battery main body 1003. However, the aluminum foil1007 is of a thin thickness (about 10 μm), and therefore, there is atendency in that moisture invasion into the battery main body 1003cannot be perfectly prevented by the aluminum foil 1007.

The fabrication of a rechargeable lithium battery having suchconfiguration as shown in FIG. 10(a) using aforesaid laminate film 1005is conducted, for instance, in the following manner. There is provided alaminate film 1005 having a prescribed length. The laminate film 1005 isdoubled along a prescribed bending line 1004 to form a folded shapehaving a space between the two bent laminate films, the battery mainbody 1003 having the two power output terminals 1001 is installed insaid space, and a heat-welded portion 1002 is formed in a peripheralportion of the folded shape having the battery main body 1003 having thetwo power output terminals 1001 enclosed therein to seal the inside. Inthis case, the peripheral portion of the folded shape in which theheat-welded portion 1002 is formed comprises the two laminate films 1005stacked. By heating the peripheral portion while applying a prescribedpressure thereto, the adjacent plastic films 1006 of the two laminatefilms 1005 are mutually heat-fused and welded to form a heat-weldedregion 1008. In this case, it is difficult to sufficiently sealneighborhood regions of the two power output terminals 1001. In order tosufficiently seal the neighborhood regions of the two power outputterminals 1001, it is necessary to increase the heat-welded portion toan extent which is greater than that required. This situation is liableto entail a problem such that the reliability of the battery isdeteriorated. Besides, in general, it is necessary for the heat-weldedportion to be provided at a width of 5 mm or more. This situationentails a decrease in the capacity density of the battery. In order toprevent the capacity density of the battery from being decreased, thereis considered to adopt a manner of bending also the peripheral portionwhich is to be heat-welded. However, to bend the peripheral portioninvolved deteriorates the reliability of the laminate film 1005, where afear of permitting moisture to be invaded into the battery main body islikely to increase.

Japanese Unexamined Patent Publication No. 213286/1997 (hereinafterreferred to as “document 1”) discloses a rechargeable battery which canmake up for such shortcomings as above described. In more detail,document 1 discloses a thin rechargeable lithium battery comprising a (abattery main body) installed in a battery vessel formed by molding athin metal plate, characterized in that said battery vessel has anopening at the face thereof in parallel to said battery main body, acover plate is disposed at said opening of the battery vessel, and saidcover plate is welded to the battery vessel by mean of laser beamwelding.

FIG. 11 is a schematic cross-sectional view illustrating the internalconstitution of the rechargeable lithium battery disclosed indocument 1. In FIG. 11, reference numeral 1100 indicates a battery mainbody disposed in a thin battery vessel 1105 whose upper face in parallelto said battery main body 1100 has an opening. Reference numeral 1104indicates a cover plate disposed so as to cover said opening, where thecover plate 1104 is welded to the battery vessel 1105 by means of laserbeam irradiation 1108 to seal the inside of the battery vessel 1105. Thebattery main body 1100 comprises a stacked body comprising a cathode1101 and an anode 1102 stacked through a separator 1103.

Document 1 describes that according to the technique described therein,it is possible to prepare a thin rechargeable lithium battery having athickness of 5 mm or less and having a relatively large area.

However, the rechargeable battery having such configuration as shown inFIG. 11 described in document 1 has disadvantages such that because thecover plate 1104 comprises a simple sheet-like plate whose thickness isthin, the cover plate 1104 is insufficient in terms of the physicalstrength, and because of this, when a stress is vertically or diagonallyapplied to the battery vessel 1105, the battery vessel is liable todeform, where there is a fear that the cathode and the anode sufferinternal shorts. Besides, there is also a disadvantage such that becauselaser beam is used when the cover plate 1104 is welded to the batteryvessel, the battery main body 1100 is unavoidably exposed to heatgenerated upon the irradiation of the laser beam, and therefore, inorder to protect the battery main body from said heat, it is necessaryto provide a heat shielding member 1106 between the battery main body1100 and a welding portion where the cover plate 1104 and the batteryvessel 1105 are welded, as shown in FIG. 11. Reference numeral 1107indicates an interstice formed when the heat shielding member 1106 isprovided.

As the heat shielding member 1106, there is used a thermally conductivemember having a thickness of about 0.1 mm and which is made of ametallic material having good thermal conductivity such as Cu, Ni or astainless steel. Because of this, when the anode or the cathode of thebattery main body comprises an anode or cathode active material which isliable to expand upon charging or discharging, or when such stress asabove described is applied to the battery vessel, the probability of theoccurrence of the internal shorts among the cathode and the anode of thebattery main body is increased. Further, since the entire thickness ofthe rechargeable lithium battery is several millimeters, the thickness(about 0.1 mm) of the heat shielding member 1106 is corresponding toseveral percentages to 5% of the entire thickness of the rechargeablelithium battery, where the capacity density of the rechargeable lithiumbattery is decreased by a quantity occupied by the heat shielding member1106. In the case where the heat shielding member 1106 is made to be ina waved form, the capacity density of the rechargeable lithium batteryis more decreased.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the foregoingsituation in the conventional thin type rechargeable lithium battery.

An object of the present invention is to provide a rechargeable lithiumbattery which is thinned without using such heat shielding member asused in the prior art.

Another object of the present invention is to provide a thin typerechargeable lithium battery in which the anode and the cathode are notinternally shorted even when charging and discharging are alternatelyrepeated over a long period of time and which excels in durability.

A further object of the present invention is to provide a thin typerechargeable lithium battery having a prolonged cycle life (a prolongedcharging and discharging cycle life).

A further object of the present invention is to provide a thin typerechargeable lithium battery which comprises a battery main bodycomprising at least a cathode, an anode, and an ion conductor enclosedbetween a pair of sealing members (a) and (b), at least said sealingmember (a) having a concave portion such that said concave portion isextended to either side of said sealing member (a) from a centralposition of said sealing member (a) so as to have a peripheral portionwhich surrounds said concave portion, and said two sealing members (a)and (b) being arranged to oppose to each other such that the face ofsaid concave portion of said sealing member (a) is faced to said sealingmember (b) through said battery main body, characterized in that saidsealing member (a) has a collar portion (a-i) at said peripheral portionof said concaved portion and said sealing member (b) has a collarportion (b-i) at a region thereof corresponding to said peripheralportion of said sealing member (a) wherein said collar portion (a-i) andsaid collar portion (b-i) are mutually welded, and either said sealingmember (a) or said sealing member (b) is provided with a power outputterminal having an electrical continuity with said battery main body andan insulating portion for insulating said power output terminal.

A further object of the present invention is to provide a process forproducing said rechargeable lithium battery. Said process typicallycomprises the steps of providing a battery main body comprising at leasta cathode, an anode, and an ion conductor, a first sealing member (a)having a concave portion with a peripheral portion surrounding saidconcave portion and a collar portion (a-i) at said peripheral portion ofsaid concave portion, and a second sealing member (b) having a collarportion (b-i) at a region thereof which is corresponding to saidperipheral portion of said first sealing member (a), arranging saidbattery main body in said concave portion of said first sealing member(a), mating said first sealing member (a) with said second sealingmember (b) to oppose to each other such that the face of said concaveportion of said first sealing member (a) is faced to said second sealingmember (b) through said battery main body, and mutually welding saidcollar portion (a-i) of said first sealing member (a) and said collarportion (b-i) of said second sealing member (b).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic slant view illustrating an example of arechargeable lithium battery of the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line X-X′ inFIG. 1, which illustrates an example of an armor member constituting therechargeable lithium battery shown in FIG. 1.

FIG. 3 is a schematic plan view of the rechargeable lithium batteryshown in FIG. 1 when viewed from above, which illustrates theconfiguration of a top face of said rechargeable lithium battery inwhich an inner pressure release vent is additionally provided.

FIG. 4 is a schematic cross-sectional view taken along the line Y-Y′ inFIG. 1, which illustrates an example of the internal constitution of therechargeable lithium battery shown in FIG. 1.

FIG. 5 is a schematic cross-sectional view taken along the line Y-Y′ inFIG. 1, which illustrates another example of the internal constitutionof the rechargeable lithium battery shown in FIG. 1 in which an innerpressure release vent is additionally provided.

FIG. 6 is a schematic explanatory view of an embodiment in that a cladmember is used when a cathode power output terminal and a cathode leadportion (extending from a cathode) are electrically connected through acathode power output terminal lead in a rechargeable lithium battery ofthe present invention.

FIG. 7 is a schematic cross-sectional view taken along the line X-X′ inFIG. 1, which illustrates an example of a battery main body accommodatedin the rechargeable lithium battery shown in FIG. 1.

FIG. 8 is a schematic plane view of a rechargeable lithium battery ofthe present invention having a battery main body having suchconfiguration as shown in FIG. 7 when viewed from above, whichillustrates the configuration of a top face of said rechargeable lithiumbattery.

FIG. 9 is a schematic view illustrating an example of a cellular phonein which a rechargeable lithium battery of the present invention isprovided.

FIGS. 10(a) and 10(b) are schematic cross-sectional views illustratingan example of a conventional rechargeable lithium battery having anarmor comprising a laminate film.

FIG. 11 is a schematic cross-sectional view illustrating another exampleof a conventional rechargeable lithium.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The present invention attains the above objects and provides a highperformance rechargeable lithium battery having improved batterycharacteristics and a prolonged cycle life (a prolonged charging anddischarging cycle life) and a process for producing said rechargeablebattery.

A typical embodiment of the rechargeable lithium battery providedaccording to the present invention comprises a battery main bodycomprising at least a cathode, an anode, and an ion conductor enclosedbetween a pair of sealing members (a) and (b), at least said sealingmember (a) having a concave portion such that said concave portion isextended to either side of said sealing member (a) from a centralposition of said sealing member (a) so as to have a peripheral portionwhich surrounds said concave portion, and said two sealing members (a)and (b) being arranged to oppose to each other such that the face ofsaid concave portion of said sealing member (a) is faced to said sealingmember (b) through said battery main body, characterized in that saidsealing member (a) has a collar portion (a-i) at said peripheral portionof said concaved portion and said sealing member (b) has a collarportion (b-i) at a region thereof corresponding to said peripheralportion of said sealing member (a) wherein said collar portion (a-i) andsaid collar portion (b-i) are mutually welded, and either said sealingmember (a) or said sealing member (b) is provided with a power outputterminal having an electrical continuity with said battery main body andan insulating portion for insulating said power output terminal.

In the rechargeable lithium battery thus constituted, the collarportions (a-i) and (b-i) which are mutually welded are situated outsidethe space formed by the concave portion of the sealing member (a) andthe sealing member (b) where the battery main body is arranged. In thisconnection, such heat shielding member required to be provided in thespace where the battery main body is arranged in the prior art is notnecessitated to be provided in the space formed by the concave portionof the sealing member (a) and the sealing member (b) where the batterymain body is arranged. Hence, the foregoing problems due to the use ofthe heat shielding member in the prior art are not occurred.Particularly, in the case where the anode or the cathode of the batterymain body comprises an anode or cathode active material which is liableto expand upon charging or discharging, even when charging anddischarging are alternately repeated over a long period of time, theanode and the cathode of the battery main body are stably maintainedwithout suffering internal shorts among them. The rechargeable lithiumbattery always exhibits satisfactory battery characteristics and has aprolonged charging and discharging cycle life.

The present invention provides a process for producing theabove-described rechargeable battery.

A typical embodiment of the process comprises the steps of:

providing a battery main body comprising at least a cathode, an anode,and an ion conductor, a first sealing member (a) having a concaveportion with a peripheral portion surrounding said concave portion and acollar portion (a-i) at said peripheral portion of said concave portion,and a second sealing member (b) having a collar portion (b-i) at aregion thereof which is corresponding to said peripheral portion of saidfirst sealing member (a),

arranging said battery main body in said concave portion of said firstsealing member (a),

mating said first sealing member (a) having said battery main bodyarranged in said concave portion of said first sealing member (a) withsaid second sealing member (b) to oppose to each other such that theface of said concave portion of said first sealing member (a) is facedto said second sealing member (b) through said battery main body, and

mutually welding said collar portion (a-i) of said first sealing member(a) and said collar portion (b-i) of said second sealing member (b).

In the process thus constituted, the collar portion (a-i) provided atthe peripheral portion of the concave portion of the first sealingmember (a) and the collar portion (b-i) provided at the region of thesecond sealing member (b) which is corresponding to said peripheralportion of the second sealing member (b) are mutually welded, thebattery main body (comprising at least the cathode, the anode, and theion conductor) accommodated in the space formed by the concave portionof first sealing member (a) and the second sealing member (b) isdesirably prevented from suffering from a thermal influence upon thewelding of the two collar portions (a-i) and (b-i). This situation makesit possible to effectively produce a thin type rechargeable lithiumbattery which excels in battery characteristics and has a prolongedcharging and discharging cycle life. In the case where the collarportion (a-i) of the first sealing member (a) and the collar portion(b-i) of the second sealing member (b) are formed by way ofmetal-processing, each of the first and second sealing members (a) and(b) which are thin becomes strengthened in terms of the physicalstrength.

In the following, the present invention will be described in more detailwith reference to the drawings.

FIG. 1 is a schematic slant view illustrating an example of arechargeable lithium battery of the present invention.

The rechargeable lithium battery shown in FIG. 1 has an sealing member101 a having a concave portion 102 a downward faced and a peripheralcollar portion 103 a surrounding said concave portion 102 a and ansealing member 101 b having a concave portion 102 b upward faced and aperipheral collar portion 103 b surrounding said concave portion 102 b,where said sealing member 101 a and said sealing member 101 b are matedsuch that said downward faced concave portion 102 a and said upwardfaced concave portion 102 b are opposed to each other and saidperipheral collar portion 103 a and said peripheral collar portion 103 bare mutually welded. In the space formed by said downward faced concaveportion 102 a and said upward faced concave portion 102 b, there isaccommodated a battery main body comprising at least a cathode, an anodeand an ion conductor (not shown). At the sealing member 101 a, there areprovided a cathode power output terminal 104 extending from the cathodeof the battery main body, an anode power output terminal 106 extendingfrom the anode of the battery main body, and an insulating portion 105for insulating said power output terminal 104 and said power outputterminal 106. Although this is not shown in the figure, if necessary, aninternal pressure release vent may be additional provided at the sealingmember 101 a through the insulating portion 105.

Here, as will be understood from FIG. 1, a combination of the sealingmember 101 a and the sealing member 101 b constitutes an armor vessel(or a battery vessel) of the rechargeable lithium battery.

In this embodiment, the concave portion (102 a, 102 b) is provided ateach of the two sealing members 101 a and 101 b. This is not limitative.The concave portion may be provided only at one of the two sealingmembers 101 a and 101 b.

The sealing member (101 a, 101 b) having such concave portion (102 a,102 b) and such collar portion (103 a, 103 b) may be prepared bysubjecting a given metallic material to deep drawing or press working.In this case, work hardening is occurred, whereby the resulting sealingmember becomes to have a satisfactory physical strength even when thethickness thereof is relatively. This provides an advantage in thatbecause the collar portions 103 a and 103 b respectively providedoutside the space formed by the concave portions 102 a and 102 b in thebattery main body is accommodated are mutually welded to establish thearmor vessel as above described, there is no occasion for heat generatedupon the welding of the collar portions 103 a and 103 b to be directlydiffused into said space, where the collar portions 103 a and 103 bfunction to radiate said heat. This situation makes it unnecessary toprovide such heat shielding member (1106) required in the conventionalthin type rechargeable lithium battery (see, FIG. 11).

The peripheral collar portion (103 a, 103 b) is desired to have a widthpreferably in a range of from 0.5 mm to 3.0 mm or more preferably in arange of from 0.5 mm to 2.0 mm. This range for the width of theperipheral collar portion (103 a, 103 b) has been established as aresult of experimental studies by the present inventors aiming atpreventing the battery main body from having a thermal influence uponthe welding.

The welding of the peripheral collar portions 103 a and 103 b may beconducted by means of laser beam welding, electron beam welding,resistance welding, or ultrasonic welding. Of these, laser beam weldingis the most appropriate in viewpoints of productivity and reliability.

The laser beam irradiation diameter upon the laser beam welding isdifferent depending upon the kind of a material constituting the sealingmember (101 a, 101 b) or the thickness of the sealing member (101 a, 101b). For instance, in the case where the sealing member (101 a, 101 b) isconstituted by a stainless steel, it is preferred to be in a range offrom 0.2 mm to 0.4 mm. In the case where the sealing member (101 a, 101b) is constituted by an aluminum, it is desired to be in a range of from0.6 mm to 0.8 mm.

In the following, description in more detail will be made of the armorvessel of the rechargeable lithium battery shown in FIG. 1 withreference to FIG. 2.

FIG. 2 is a schematic cross-sectional view taken along the line X-X′ inFIG. 1, which illustrates the armor vessel (comprising the sealingmember 101 a and the sealing member 101 b) constituting the rechargeablelithium battery shown in FIG. 1. In FIG. 2, the components of thebattery main body are omitted.

In FIG. 2, reference numeral 101 indicates the sealing member (101 a,101 b) in FIG. 1, reference numeral 102 indicates the concave portion(102 a, 102 b) in FIG. 1, and reference numeral 103 indicates theperipheral collar portion (103 a, 103 b) in FIG. 1.

It is preferred for the concave portion 102 [that is, the concaveportion (102 a, 102 b) in FIG. 1] to be shaped to have a cross sectionin a substantially symmetrical trapezoidal form. The symmetricaltrapezoidal form as the concave portion 102 has a desired depth 201. Thesymmetrical trapezoidal form as the concave portion 102 is preferred tohave an inclination 202 in a range of from 5° to 45°.

However, the concave portion 102 may be of a cross section in anunsymmetrical trapezoidal form.

For the depth 201 of the concave portion 102 in the symmetricaltrapezoidal form of the sealing member 101 [that is, the sealing member(101 a, 101 b) in FIG. 1], it is not strictly defined. However, ingeneral, it is preferably in a range of from 0.3 mm to 3 mm or morepreferably in a range of from 0.5 mm to 2.5 mm. This range for the depth201 of the concave portion 102 has been established as a result ofexperimental studies by the present inventors. Particularly, in the casewhere the depth 201 is made to be less than 0.3 mm, the thickness of thesealing member 101 becomes to be relatively excessively thick, where thespace for the battery main body to be accommodated becomes smallaccordingly. Thus, the depth 201 is necessary to be 0.3 mm or more. Tomake the depth 201 to be beyond 3 mm is not suitable for attaining theobject of the present invention to provide a thin type rechargeablelithium battery.

For the constituent of the sealing member 101 [that is, the sealingmember (101 a, 101 b) in FIG. 1], a stainless steel having a largephysical strength is preferred in the case where the sealing member 101is required to be relatively thinned. An aluminum material is preferredin the case where the sealing member 101 is required to be relativelylightened. Besides, it is possible to use other metallic materials suchas a nickel material, a nickel-plated iron material, a copper material,and the like.

For the thickness of the sealing member 101 [that is, the sealing member(101 a, 101 b) in FIG. 1], it is preferred to be in a range of from 0.05to a thickness for which press working can be conducted. For the upperlimit of the thickness of the sealing member 101, it is 0.3 mm in thecase where the sealing member 101 is constituted by a stainless steelmaterial, and it is 0.8 mm in the case where the sealing member 101 isconstituted by an aluminum material. Specifically, in a preferredembodiment, the thickness of the sealing member 101 is in a range offrom 0.1 mm to 0.2 mm in the case where the sealing member 101 isconstituted by a stainless steel material. And in the case where thesealing member 101 is constituted by an aluminum material, the thicknessof the sealing member is in a range of from 0.2 mm to 0.5 mm.

Separately, depending upon the situation involved, it is possible forthe sealing member 101 to be constituted by a plastic material. However,in practice, it is difficult to constitute the entirety of the sealingmember 101 by a plastic material because the plastic material does nothave a satisfactory physical strength required for the sealing member.

A plastic material may be used in such configuration as shown in FIG. 3of the rechargeable lithium battery of the present invention. FIG. 3 isa schematic plan view of the rechargeable lithium battery shown in FIG.1 when viewed from above, which illustrates the configuration of a topface of said rechargeable lithium battery in which an inner pressurerelease vent is additionally provided.

In FIG. 3, reference numeral 101 indicates the sealing member (101 a) inFIG. 1, and reference numeral 103 indicates the peripheral collarportion (103 a) in FIG. 1. Reference numeral 104 indicates the cathodepower output terminal (104) in FIG. 1, reference numeral 105 indicatesthe insulating portion (105) in FIG. 1, and reference numeral 106indicates the anode power output terminal (106) in FIG. 1. Referencenumeral 301 indicates an inner pressure release vent which serves torelease the inner pressure in the inside of the armor vessel (thebattery vessel) when said inner pressure is increased. As shown in FIG.3, on the outer surface of the sealing member 101 of the rechargeablelithium battery, there are provided the anode power output terminal 106,the cathode power output terminal 104, and the inner pressure releasevent 301 through the insulating portion 105, where the insulatingportion 105 may be constituted by a plastic material, and the innerpressure release vent 301 may be also constituted by a plastic material.

FIG. 4 is a schematic cross-sectional view taken along the line Y-Y′ inFIG. 1, which illustrates an example of the internal constitution of therechargeable lithium battery shown in FIG. 1. In FIG. 4, referencenumeral 101 a indicates the sealing member (101 a) in FIG. 1, referencenumeral 101 b indicates the sealing member (101 b) in FIG. 1, referencenumeral 104 indicates the cathode power output terminal (104) in FIG. 1,reference numeral 105 indicates the insulating portion (105) in FIG. 1,and reference numeral 106 indicates the anode power output terminal(106) in FIG. 1. Each of reference numerals 401 and 402 indicates ansupport metal plate inserted in the insulating portion 105 such that thesupport metal plate is fixed to the insulating portion. Each of thesupport metal plates 401 and 402 is fixed to the sealing member 101 a bymeans of laser beam welding 405. Reference numeral 403 indicates aterminal lead connected to the cathode power output terminal 104, andreference numeral 404 indicates a terminal lead connected to the anodepower output terminal 106, where each of the terminal leads 403 and 404is electrically isolated from the sealing member 101 b through theinsulating portion 105. Similarly, the cathode power output terminal 104and the anode power output terminal 106 are also electrically isolatedfrom the sealing member 101 a through the insulating portion 105.

In this constitution shown in FIG. 4, the insulating portion may beconstituted by a plastic material.

FIG. 5 is a schematic cross-sectional view taken along the line Y-Y′ inFIG. 1, which illustrates another example of the internal constitutionof the rechargeable lithium battery shown in FIG. 1. The constitutionshown in FIG. 5 is the same as that shown in FIG. 4, except for thefollowing points. That is, in the constitution shown in FIG. 5, suchsupport mental plate (401) used in FIG. 4 is not used, the insulatingportion 105 is directly fixed to the sealing member 101 a by partiallyinserting the sealing member 101 a in the insulating portion 105, and aninternal pressure release vent 301 is provided at the insulating portion105. The internal pressure release vent 301 serves to release theinternal pressure of the rechargeable lithium battery when said internalpressure is undesirably increased. In this embodiment, the internalpressure release vent 301 comprises a plug comprising a thin film formedof a plastic material which is the same as the constituent of theinsulating portion 105.

In the constitution shown in FIG. 5, the sealing members 101 a and 101b, the cathode power output terminal 104 having the terminal lead 403,the anode power output terminal 106 having the terminal lead 404, andthe insulating portion 105 having the internal pressure release vent 301may be integrally formed.

The internal pressure release vent 301 is not limited only to aforesaidembodiment. The plug comprising the plastic material as the internalpressure release vent 301 may be a metal thin foil fixed to theinsulating portion 105 so that said metal thin foil can be automaticallybroken to release the inner pressure of the rechargeable lithium batterywhen said inner pressure is increased to reach a given pressure.Alternatively, it is possible to form a thin metal film portion at thesealing member 101 a by way of press working so that said thin metalfilm portion can function as the internal pressure release vent 301.Besides, the internal pressure release vent 301 may comprise a rubberplug (in a spherical form or a trapezoidal form) or a spring whichactuates to release the inner pressure of the rechargeable lithiumbattery when said inner pressure is increased to reach a given pressure.

FIG. 6 is a schematic explanatory view of an embodiment in that a cladmember is used when a cathode power output terminal and a cathode leadportion (extending from a cathode) are electrically connected through acathode power output terminal lead in a rechargeable lithium battery ofthe present invention. In FIG. 6, reference numeral 104 indicates acathode power output terminal (104) [see, FIG. 1, FIG. 4, or FIG. 5],and reference numeral 403 indicates a cathode power output terminal lead(403) [see, FIG. 4 or FIG. 5]. Reference numeral 601 indicates a cathodelead portion extending from a cathode 602 of a battery main body (notshown) provided in a rechargeable lithium battery (not shown) havingsuch configuration as shown in FIG. 1.

The cathode power output terminal 104 is preferred to comprises a highlyelectrically conductive metallic material which is hardly corroded andhas a satisfactory physical strength. Such metallic material can includea metal member made of Cu or Ni, and a member comprising said metalmember which is plated with Au. When the cathode power output terminallead 403 which is integrally formed with the cathode lead portion 601extending from the cathode 602 is constituted by a single metallicmaterial, there will be such disadvantages as will be described in thefollowing. In the case where both the cathode lead portion 601 and thecathode power output terminal lead 403 are constituted by an aluminummaterial, although they can be readily welded with each other, it isdifficult to secure a satisfactory physical strength for the cathodepower output terminal lead 403 which is integrated with the cathode leadportion 601. In the case where the cathode power output terminal lead403 is constituted by a nickel material having a satisfactory physicalstrength and the cathode lead portion 601 is constituted by an aluminummaterial, it is difficult for the cathode power output terminal lead 403and the cathode lead portion 601 to be welded so that the integratedportion between them is always maintained without being peeled. In orderto eliminate these disadvantages, it is preferred that the cathode poweroutput terminal lead 403 is constituted a clad member comprising acomposite which comprises two or more kinds of metal or alloy materials.This situation is similar also with respect to the anode.

FIG. 7 is a schematic cross-sectional view taken along the line X-X′ inFIG. 1, which illustrates an example of a battery main body accommodatedin the rechargeable lithium battery shown in FIG. 1. In FIG. 7,reference numeral 700 indicates a battery main body accommodated in thearmor vessel (the battery vessel) formed by mating the two sealingmembers 101 a and 101 b each having the concave portion 102 (having across section in a symmetrical trapezoidal form with a depth 201) andthe peripheral collar portion 103 such that the two symmetricaltrapezoidal form spaces of the two concave portions 102 are faced tooppose to each other and welding the two peripheral collar portion 103with each other. The battery main body 700 comprises a stacked bodyformed by winding an anode 702 and a cathode 602 (see, FIG. 6) throughan isolator 701 (comprising an ion conductor comprising an electrolyteor a separator impregnated with an electrolyte solution) about a givenaxis and an insulating film 703 which covers said stacked body.

In the following, description will be made of each constituent of thebattery main body 700 shown in FIG. 7.

Cathode 602:

The cathode 602 comprises at least a cathode active material and acathode collector. The cathode active material may comprise a materialcapable of taking lithium therein and releasing said lithium and whichis insoluble in and stable against an electrolyte solution used in therechargeable lithium battery. Such material as the cathode activematerial can include lithium-containing transition metal oxides such asLiCoO₂, LiNiO₂, LiMnO₂, and LiMn₂O₄; metal oxides containing no lithiumsuch as V₂O₅, MnO₂, TiO₂, and MoO₃; and metal chalcogen compounds suchas TiS₂, and MoS₂. Besides, electrically conductive polymers such aspolyacetylene, polypyrrole, polyaniline, and polyphthalocyanine, andderivatives of these polymers are also usable.

The cathode 602 may be prepared by forming a cathode active materiallayer on a collector using such cathode active material, if necessary byadding an appropriate electrically conductive auxiliary or/and anappropriate binder. The cathode active material layer may be formed oneither one side or opposite sides of the collector.

The collector used in the cathode serves to efficiently supply anelectric current consumed in or collect an electric current generated inthe electrode reaction upon charging or discharging. In this connection,the collector is constituted by a material which is highly electricallyconductive and inactive in the battery reaction.

Such material to constitute the collector of the cathode can includemetals such as Al, Ti, and Ni, and alloys of these metals such asstainless steels. The collector may be shaped in a sheet form, meshform, porous form-like sponge, expanded metal form, or punched metalform.

The electrically conductive auxiliary which is used if required upon theformation of the cathode can include electrically conductive materialswhich are highly electrically conductive and are insoluble in and stableagainst an electrolyte solution used in the rechargeable lithiumbattery. Specific examples of such electrically conductive material arecarbonous materials such as powdery graphite structure carbon, and thelike, and powdery metallic materials such as copper powder, aluminumpowder, titanium powder, and the like.

As the binder which is used if required upon the formation of thecathode, it is preferred to use an organic polymer which has adhesiveproperties and which is insoluble in and stable against an electrolytesolution used in the rechargeable lithium battery. As specificpreferable examples of such organic polymer, there can be mentionedfluororesins such as poly(vinylidene fluoride), tetrafluoroethylenepolymer, and the like. Besides, celluloses such as methyl cellulose andcarboxymethyl cellulose, and polyvinyl series materials such aspolyvinyl alcohol, and the like are also usable.

Anode 702:

The anode 702 comprises at least an anode active material and an anodecollector. The anode active material may comprise a material capable oftaking lithium therein and releasing said lithium and which is insolublein and stable against an electrolyte solution used in the rechargeablelithium battery. Such material as the anode active material can includea lithium metal, and lithium-containing alloys such as Al—Li alloy,Pb—Li alloy, Sn—Li alloy, and the like. Besides, metal oxides such asTiO₂ and V₂O₅; lithium compounds of these oxides; alloys comprising ametal (Sn or Si) capable of alloying with lithium and a metal (Fe, Co,or Ni) incapable of alloying with lithium such as Sn—Fe alloy, Sn—Coalloy, Si—Fe alloy, and Si—Ni alloy; and carbonous materials such asamorphous carbon and graphite.

The anode 702 may be prepared by forming an anode active material layeron a collector using such anode active material, if necessary by addingan appropriate electrically conductive auxiliary or/and an appropriatebinder. The anode active material layer may be formed on either one sideor opposite sides of the collector.

The collector used in the anode serves to efficiently supply an electriccurrent consumed in or collect an electric current generated in theelectrode reaction upon charging or discharging. In this connection, thecollector is constituted by a material which is not alloyed with lithiumand which is highly electrically conductive and inactive in the batteryreaction.

Such material to constitute the collector of the anode can includemetals such as Cu, Ni, and Ti, and alloys of these metals such asstainless steels. The collector may be shaped in a sheet form, meshform, porous form-like sponge, expanded metal form, or punched metalform.

The electrically conductive auxiliary which is used if required upon theformation of the anode can include electrically conductive materialswhich are highly electrically conductive and are insoluble in and stableagainst an electrolyte solution used in the rechargeable lithiumbattery. Specific examples of such electrically conductive material arecarbonous materials such as powdery graphite structure carbon, and thelike, and powdery metallic materials such as copper powder, aluminumpowder, titanium powder, and the like.

As the binder which is used if required upon the formation of the anode,it is preferred to use an organic polymer which has adhesive propertiesand which is insoluble in and stable against an electrolyte solutionused in the rechargeable lithium battery. As specific preferableexamples of such organic polymer, there can be mentioned fluororesinssuch as poly(vinylidene fluoride), tetrafluoroethylene polymer, and thelike. Besides, celluloses such as methyl cellulose and carboxymethylcellulose, and polyvinyl series materials such as polyvinyl alcohol, andthe like are also usable.

Isolator 701:

The isolator 701 is provided in order to electrically isolating betweenthe cathode 602 and the anode 702, where it is required for the isolatorto allow lithium ion to freely pass therethrough. As the isolator 701,it is possible to use a separator having an electrolyte solution (asupporting electrolyte solution) obtained by dissolving a givenelectrolyte (a given supporting electrolyte) in an adequate solventretained therein. In this case, the separator functions as an ionconductor.

Besides, the isolator 701 may comprise an ion conductor comprising asolid electrolyte or a solidified electrolyte. In this case, it ispossible for said solid electrolyte or said solidified electrolyte to beretained by a separator.

In the case where the separator is used, the separator is necessary tohave a structure having a number of perforations capable of allowingions of the electrolyte to pass therethrough and it is also necessary tobe insoluble in and stable to the electrolyte solution.

Therefore, the separator is necessary to comprise a member whichsatisfies these requirements. As such member, there can be mentioned,for example, nonwoven fabrics or membranes having a micropore structure,made of polyolefin such as polypropylene, polyethylene or the like.Besides, composite members comprising two or more these members having aplurality of micropores are also usable.

The electrolyte solution comprises a given electrolyte dissolved in agiven solvent. The electrolyte can include lithium hexafluorophosphate,lithium tetrafluorophosphate, and lithium tetrafluoroborate. The solventcan include propylene carbonate, ethylene carbonate, diethyl carbonate,methylethyl carbonate, and γ-butyrolactone.

The solidified electrolyte can include those obtained by providing anelectrolyte solution obtained by dissolving any of aforesaidelectrolytes in any of aforesaid solvents and gelling said electrolytesolution by a gelling agent to solidify the electrolyte solution. As thegelling agent, there can be used a polymer selected from a groupconsisting of polyethylene oxide, polyacrylonitrile, andpolyethylene-imine.

The solid electrolyte can include β-alumina, silver oxide, and lithiumiodide.

For the arrangement of the cathode, the anode and the ion conductor(comprising the separator (which is eventually impregnated with theelectrolyte solution), the solid electrolyte, the solidifiedelectrolyte, or a combination of the separator (not impregnated with theelectrolyte solution) and the solid electrolyte or the solidifiedelectrolyte) in the preparation of a battery main body, there can beadopted a configuration in that the cathode and the anode arealternately stacked through the ion conductor or a configuration in thatthe cathode and the anode are wound through the ion conductor separatorin a flat form. In the case where the ion conductor comprising theseparator (which is eventually impregnated with the electrolytesolution) is used, a wound configuration in a flat form is desirable. Inthe case where the ion conductor comprising the solid electrolyte or thesolidified electrolyte is used, a stacked configuration is desirable.

Insulating Film 703:

The insulating film 703 which covers the battery main body 700 isdesired to comprise an insulating organic material which is resistant tosolvents. Such organic material can include polypropylene, polyethylene,polyethylene terephthalate, polyimide, and fluororesin.

The insulating film 703 is preferred to have a thickness in a range offrom 10 μm to 50 μm.

FIG. 8 is a schematic plane view of a rechargeable lithium battery ofthe present invention having a battery main body having suchconfiguration as shown in FIG. 7 when viewed from above, whichillustrates the configuration of a top face of said rechargeable lithiumbattery.

In FIG. 8, reference numeral 101 indicates an upper sealing member(which is corresponding to the sealing member 101 a in FIG. 7).Reference numeral 802 indicates a battery main body (which iscorresponding to the battery main body 700 in FIG. 7). Reference numeral601 indicates a cathode lead portion (which is corresponding to thecathode lead portion 601 in FIG. 6) which is extending from the cathodeof the battery main body 802. Reference numeral 801 indicates an anodelead portion extending from the anode of the battery main body 802.Reference numeral 105 indicates an insulating portion (see, FIG. 4 orFIG. 5) through which an inner pressure release vent 301, a cathodepower output terminal 104, and an anode power output terminal 106 areprovided. The cathode lead portion 601 is electrically connected to thecathode power output terminal 104 through a cathode power outputterminal lead 403, and the anode lead portion 801 is electricallyconnected to the anode power output terminal 106 through an anode poweroutput terminal lead 404.

The insulating portion 105 comprises an insulating plastic materialhaving a satisfactory physical strength and which excels in resistanceto solvents and does not allow moisture to pass therethrough. Specificexamples of such plastic material are polyethylene, polypropylene,polyethylene terephthalate, and fluororesin.

As previously described, the inner pressure release vent 301 may beformed upon integrally forming the insulating portion 105 with thecathode power output terminal 104 and the anode power output terminal106.

Now, when the battery main body 802 [comprising the cathode, the anode,the isolator (containing the ion conductor)] is accommodated in thesealing member 101 constituting the battery vessel (the armor vessel),it is necessary for the battery main body 802 to be insulated from thesealing member 101 so that the battery main body 802 is not directlycontacted with the sealing member 101. This purpose can be attained by amethod of previously covering the battery main body 802 by an insulatingfilm made of polyimide, polyethylene terephthalate, polypropylene, orpolyethylene; a method of previously lining the inside face of thesealing member 101 by an insulating plastic film; or a method ofpreviously coating the inside face of the sealing member 101 by aninsulating plastic material.

A rechargeable lithium battery constituted as above described may beproduced, for instance, in the following manner. For instance, suchconfiguration as shown in FIG. 4 in that the cathode power outputterminal 104 and the anode power output terminal 106 are embedded in theinsulating portion 105 is first established at a prescribed position inthe concave portion 102 (having a cross section in a symmetricaltrapezoidal form with a depth 201) of the upper sealing member 101(corresponding to the sealing member 101 a in FIG. 7). Then, the batterymain body 802 covered by an insulating plastic film is arranged in saidconcave portion 102, where the cathode lead portion 601 of the batterymain body 802 is connected with the cathode power output terminal 104 byway of laser beam welding, resistance welding, or ultrasonic welding,and the anode lead portion 801 of the battery main body 802 is alsoconnected with the anode power output terminal 106 by way of laser beamwelding, resistance welding, or ultrasonic welding. Then, the lowersealing member 101 b having the concave portion 102 (having a crosssection in a symmetrical trapezoidal form with a depth 201) is matedwith the upper sealing member 101 a so that the symmetrical trapezoidalform space of the concave portion 102 of the sealing member 101 b andthe symmetrical trapezoidal form space (having the battery main body 802arranged therein) of the concave portion 102 of the sealing member 101aare opposed to each other. And the two peripheral collar portions 103(see, FIG. 7) of the two sealing members 101 a and 101 b which are matedare mutually welded. By this, there is obtained a thin type rechargeablelithium battery is obtained.

Incidentally, there is considered a manner of conducting the joining ofthe two peripheral collar portions 103 in the above using an adhesive.Particularly, in the case where the rechargeable lithium battery is usedunder environmental condition which is maintained at about normaltemperature, it is possible that the joining of the two peripheralcollar portions 103 in the production of the rechargeable lithiumbattery is conducted using an appropriate adhesive. However, in the casewhere the rechargeable lithium battery is used under environmentalcondition with low temperature or high temperature, the joining of thetwo peripheral collar portions 103 using an adhesive is not suitable forthe reason that because the expansion coefficient of the adhesive isdifferent from that of the peripheral collar portions, there is atendency in that the adhesion between the adhesive and the peripheralcollar portions is decreased to allow moisture invasion into the insideof the battery, resulting in deteriorating the battery performance.

On the other hand, in the case where the two peripheral collar portions103 are joined by welding them by way of laser beam welding, theportions to be mutually joined of the two peripheral collar portions arefused and joined in a uniform state. In this connection, the resultingrechargeable lithium battery has a tightly sealed structure whichsufficiently endures against environmental changes including temperaturechanges to a large extent and has an improved durability and an improvedreliability.

FIG. 9 is a schematic view illustrating an example when a rechargeablelithium battery of the present invention is practically used as a powersource in a cellular phone. In FIG. 9, reference numeral 901 indicates arechargeable lithium battery of the present invention, and referencenumeral 902 a cellular phone. As shown in FIG. 9, the rechargeablelithium battery 901 is set to the cellular phone 902 so that the outsideof the sealing member of the rechargeable lithium battery 901constitutes part of the armor of the cellar phone 902. In this case, inorder for the outside of the rechargeable lithium battery 901 to bematched with the armor of the cellar phone 902 so that an exteriordifference is not present between them, it is desired that anappropriate plastic material or a label is affixed to or coating isapplied to the exterior of the rechargeable lithium battery. Therechargeable lithium battery of the present invention can be used as itis without conducting a reinforcing treatment for the armor thereofbecause it has a sufficient physical strength. On the other hand, in thecase where a conventional rechargeable battery whose armor comprising alaminate film is installed in the cellular phone, because the armorcomprising the laminate film is inferior in the physical strength, it isnecessary to conduct a reinforcing treatment for the armor.

In the following, the present invention will be described in more detailwith reference to examples. It should be understood that these examplesare only for illustrative purposes and that the scope of the presentinvention is not restricted to these examples.

EXAMPLE 1

In this example, there was prepared a thin type rechargeable lithiumbattery having such configuration as shown in FIGS. 1 to 4 in thefollowing manner.

1. Preparation of Cathode:

90 parts by weight of LiCoO₂ as a cathode active material, 5 parts byweight of natural graphite as an electrically conductive auxiliary, and5 parts by weight of polyvinylidene fluoride as a binder were mixed toobtain a mixture. The mixture was mixed with 50 parts by weight ofN-methyl-2-pyrrolidone as a solvent to obtain a paste having a viscosityof 3000 cps. The past was applied onto opposite sides of an aluminumfoil having a thickness of 20 μm as a collector, followed by subjectingto drying thereby to form a coat layer on each of the opposite sides ofthe aluminum foil.

The resultant obtained in the above was subjected to pressing to obtainan element having a thickness of 200 μm which comprises the aluminumfoil sandwiched between the two layers each as a cathode active materiallayer. The element thus obtained was cut to obtain six cathodes having asize of 52 mm×70 mm which are used in the formation of six cell unitseach comprising a separator sandwiched between a cathode and an anodeupon the preparation of a battery main body, which will be describedlater.

2. Preparation of Anode:

95 parts by weight of graphite as an anode active material and 5 partsby weight of polyvinylidene fluoride as a binder were mixed to obtain amixture. The mixture was mixed with 60 parts by weight ofN-methyl-2-pyrrolidone as a solvent to obtain a paste having a viscosityof 2000 cps. The past was applied onto opposite sides of a copper foilhaving a thickness of 12 μm as a collector, followed by subjecting todrying thereby to form a coat layer on each of the opposite sides of thealuminum foil.

The resultant obtained in the above was subjected to pressing to obtainan element having a thickness of 180 μm which comprises the copper foilsandwiched between the two layers each as an anode active materiallayer. The element thus obtained was cut to obtain seven anodes having asize of 52 mm×70 mm which are used in the formation of six cell unitseach comprising a separator sandwiched between a cathode and an anodeupon the preparation of a battery main body, which will be describedlater.

3. Preparation of Battery Main Body:

(1). For each of the six cathodes obtained in the above step 1, apartial portion of each of the two cathode active material layers wasremoved to expose the collector (the aluminum foil), and an aluminumribbon having a width of 5 mm, a thickness of 50 μm, and a length of 5mm as a cathode lead was welded to the exposed portion of the collector.

(2). For each of the seven anodes obtained in the above step 2, apartial portion of each of the two anode active material layers wasremoved to expose the collector (the copper foil), and a copper ribbonhaving a width of 5 mm, a thickness of 50 μm, and a length of 5 mm as ananode lead was welded to the exposed portion of the collector.

(3). The seven anodes obtained in the above (2) and the six cathodesobtained in the above (1) were alternately stacked through a separatorcomprising a 25 μm polyethylene porous film having a number ofmicropores and having a size of 53 mm×71 mm each time so that the anodewas situated on either outermost side, whereby a stacked battery mainbody was obtained. And a 25 μm thick polypropylene film having a size of53 mm×71 mm as an insulating film was fixed to each of the oppositeouter sides of the battery main body in order to insulating the batterymain body from a battery vessel (an armor vessel) in which the batterymain body is accommodated.

4. Preparation of Sealing Members:

There were prepared two sealing members (101 a and 101 b, see FIG. 1)each having such cross section pattern as shown in FIG. 2 by processinga stainless steel plate having a thickness of 0.15 mm by way of deepdrawing using a die. Particularly, there were prepared a rectangularpan-like shaped sealing member (a) and a rectangular pan-like shapedsealing member (b) each having a concave portion shaped to have a crosssection in a substantially symmetrical trapezoidal form and a flatperipheral collar portion surrounding said concave portion, said concaveportion having a rectangular bottom having a longitudinal length of 85.2mm and a lateral length of 53.2 mm and a rectangular open top having alongitudinal length of 86 mm and a lateral length of 54 mm, said flatperipheral collar portion having a width of 2 mm, said symmetricaltrapezoidal form as said concave portion having a depth (the verticallength of the symmetrical trapezoidal form) of 1.65 mm, and saidsymmetrical trapezoidal form as said concave portion having aninclination (202, see FIG. 2) of 15°. The peripheral collar portion ofthe sealing member (a) will be hereinafter referred to as “peripheralcollar portion (a-i)”, and the peripheral collar portion of the sealingmember (b) will be hereinafter referred to as “peripheral collar portion(b-i)”.

5. Fabrication of Rechargeable Battery:

(1). For the sealing member (a) obtained in the above step 4, an openingof a size of 12 mm×10 mm was formed at a prescribed end portion of theconcave portion. In the space established in the concave portion of thesealing member (a) by said opening, using a jig having a die, a fusedpolypropylene material was introduced and a 150 μm thick nickel sheet(i) as a cathode power output terminal and a 150 μm thick nickel sheet(ii) as an anode power output terminal were separately inserted in saidfused polypropylene material, followed by being cooled. By this, in thespace established in the concave portion of the sealing member (a) bythe opening, there was formed an insulating portion (comprising thepolypropylene material) having the cathode power output terminal[comprising the nickel sheet (i)] and the anode power output terminal[comprising the nickel sheet (ii)] spacedly arranged such that their endportions are separately exposed to the outside from the upper face ofthe insulating portion which is situated in the opening of the concaveportion and the remaining their end portions are also exposed to theoutside from the lower side face of the insulating portion which issituated in the inside of the concave portion. Here, the cathode poweroutput terminal and the anode power output terminal including theirexposed end portions are electrically isolated from the sealing member(a) by the insulating portion.

(2). The battery main body obtained in the above step 3 was arranged inthe remaining space of the concave portion of the sealing member (a),where the cathode leads (comprising the aluminum ribbon) of the batterymain body were together fixed to the cathode power output terminalexposed from the lower side face of the insulating portion by way ofultrasonic welding, and the anode leads (comprising the copper ribbon)of the battery main body were together fixed to the anode power outputterminal exposed from the lower side face of the insulating portion byway of ultrasonic welding. Then, an electrolyte solution obtained bydissolving 1 M (mol/liter) of lithium hexafluorophosphate dissolved in 1liter of a mixed solvent obtained by mixing propylene carbonate anddimethyl carbonate at an equivalent mixing ratio was introduced in thebattery main body to impregnate the separators of the battery main bodywith the electrolyte solution.

Thereafter, the sealing member (b) was mated with the sealing member (a)such that the symmetrical form concave portion of the sealing member (b)and the symmetrical form concave portion (having the battery main bodyand the insulating portion therein ) of the sealing member (a) werematched to oppose to each other to obtained a battery vessel comprisingthe sealing member (a) and the sealing member (b) in which the batterymain body is enclosed and which has a peripheral collar portioncomprising the peripheral collar portion (a-i) and the peripheral collarportion (b-i) which are mated.

(3). The battery vessel obtained in the above (2) was positioned on anX-Y table capable of being freely moved in an X-axis direction and alsoin a Y-axis direction, and while retaining the peripheral collar portion[comprising the peripheral collar portion (a-i) and the peripheralcollar portion (b-i)] of the battery vessel by means of a retaining jig,the peripheral collar portion (a-i) and the peripheral collar portion(b-i) constituting the peripheral collar portion of the battery vesselwere intermittently welded at an interval of 2 mm by means of a YAGlaser welding machine at an energy of 1.4 J, a pulse irradiation time of2 m·second, and a pulsating frequency of 1 pps (pulse per second) whilemoving the X-Y table. Thereafter, the retaining jig was detached, andthe welding by the YAG laser welding machine was conducted for theentirety of the peripheral collar portion (a-i) and the peripheralcollar portion (b-i) at an energy of 1.4 J, a pulse irradiation time of2 m·second, and a pulsating frequency of 25 pps while moving the X-Ytable at a moving speed of 2.0 mm/second, whereby the peripheral collarportion (a-i) and the peripheral collar portion (b-i) constituting theperipheral collar portion of the battery vessel were sufficiently weldedto tightly seal the peripheral collar portion of the battery vessel.

Thus, there was obtained a thin type rechargeable lithium battery.

In this way, there were prepared six thin type rechargeable lithiumbatteries.

EXAMPLE 2

The procedures of Example 1 were repeated, except that the preparationof the anode in the step 2 in Example 1 was conducted as will bedescribed below, to obtain five thin type rechargeable lithiumbatteries.

Preparation of Anode:

60 parts by weight of a powdery tin material having an average particlesize of 3 μm as an anode active material and 5 parts by weight ofcarboxymethyl cellulose as a binder were mixed to obtain a mixture. Themixture was mixed with 35 parts by weight of deionized water as asolvent to obtain a paste having a viscosity of 2000 cps. The past wasapplied onto opposite sides of a copper foil having a thickness of 12 μmas a collector, followed by subjecting to drying thereby to form a coatlayer on each of the opposite sides of the aluminum foil. The resultantobtained was subjected to pressing to obtain an element having athickness of 180 μm which comprises the copper foil sandwiched betweenthe two layers each as an anode active material layer. The element thusobtained was cut to obtain seven anodes having a size of 52 mm×70 mm,which were used in the formation of six cell units each comprising aseparator sandwiched between a cathode and an anode upon the preparationof a battery main body.

EXAMPLE 3

The procedures of Example 1 were repeated, except that without using theseparators and the electrolyte solution, a solidified electrolytematerial layer was formed on the surface of each cathode and also on thesurface of each anode as will be described below, to obtain five thintype rechargeable lithium batteries.

On the opposite surfaces of each of six cathodes having a size of 52mm×70 mm prepared in the same manner as in the step 1 in Example 1 andalso on the opposite surfaces of each of seven anodes having a size of52 mm×70 mm prepared in the same manner as in the step 2 in Example 1, acoating liquid obtained by mixing 70 parts by weight ofmethoxypolyethylene glycol monoacrylate and 30 parts by weight ofpolyethylene glycol dimetacrylate to obtain a mixture and mixing saidmixture with 400 parts by weight of an electrolyte solution obtained bydissolving 1 M (mol/liter) of lithium hexafluorophosphate dissolved in 1liter of a mixed solvent obtained by mixing ethylene carbonate anddimethoxy ethane at an equivalent mixing ratio and 0.3 part by weight of2,2-dimethoxy-2-phenylacetophenone was applied, followed by subjectingto irradiation of ultraviolet rays, whereby a solidified electrolytematerial layer having a thickness of 12.5 μm [this thickness iscorresponding to a half of the thickness (25 μm) of the polypropyleneporous film as the separator used in the step 3-(3) in Example 1] oneach of the opposite surfaces of each of the six cathodes and also oneach of the opposite surfaces of each of the seven anodes.

The remaining procedures were conducted as in Example 1.

EXAMPLE 4

The procedures of Example 1 were repeated, except for the followingpoint, to obtain five thin type rechargeable lithium batteries.

In the step 5-(2) in Example 1, when the cathode leads (comprising thealuminum ribbon) of the battery main body were together fixed to thecathode power output terminal exposed from the lower side face of theinsulating portion by way of ultrasonic welding, a 50 μm thick cladmember comprising an aluminum layer and a nickel layer stacked was fixedto the cathode power output terminal by welding the nickel layer sidethereof with the cathode power output terminal by way of ultrasonicwelding and the aluminum layer side of the clad member was welded withthe cathode leads (comprising the aluminum ribbon) by way of ultrasonicwelding.

The remaining procedures were conducted as in Example 1.

COMPARATIVE EXAMPLE 1

In this comparative example, there was prepared a thin type rechargeablelithium battery having such configuration as shown in FIG. 11 in thefollowing manner.

The procedures of the steps 1 to 3 in Example 1 were repeated to obtaina battery main body (1100).

There was prepared a battery vessel (1105) by processing a 0.5 mm thickstainless steel plate by way of deep drawing using a die.

The battery main body (1100) obtained in the above was accommodated inthe battery vessel (1105). Then, a 0.1 mm thick heat shielding member(1106) made of stainless steel was arranged on the battery main body(1100) as shown in FIG. 11. Thereafter, an electrolyte solution obtainedby dissolving 1 M (mol/liter) of lithium hexafluorophosphate dissolvedin 1 liter of a mixed solvent obtained by mixing propylene carbonate anddimethyl carbonate at an equivalent mixing ratio was introduced into thebattery vessel (1105) to impregnate the separators (1103) of the batterymain body (1100) with the electrolyte solution.

Thereafter, a cover (1104) having a terminal takeout opening was cappedon the battery vessel (1105), and the cover (1104) was welded with thebattery vessel (1105) using a YAG laser welding machine.

In the above, it was made possible to separately take out the cathodeleads and the anode leads of the battery main body (1100) through theterminal takeout opening of the cover (1104). The cathode leads and theanode leads of the battery main body (1100) were taken out through theterminal takeout opening of the cover (1104) to form a pair of poweroutput terminals. To insulate the terminals from the battery vessel wasconducted by spraying a liquefied polyethylene resin to the terminals.

Thus, there was obtained a thin type rechargeable lithium battery havingsuch configuration as shown in FIG. 11.

In this way, there were prepared six thin type rechargeable lithiumbatteries.

COMPARATIVE EXAMPLE 2

The procedures of Comparative Example 1 were repeated, except that theanodes of the battery main body (1100) were prepared in the same manneras in Example 2, to obtain five thin type rechargeable lithiumbatteries.

COMPARATIVE EXAMPLE 3

The procedures of Comparative Example 1 were repeated, except thatwithout using the separators and the electrolyte solution, a solidifiedelectrolyte material layer was formed on each of the opposite surfacesof each of the cathodes and also on each of the opposite surfaces ofeach of the anodes in the same manner as in Example 3, to obtain fivethin type rechargeable lithium batteries.

COMPARATIVE EXAMPLE 4

The procedures of Comparative Example 1 were repeated, except that noheat shielding member was used, to obtain six thin type rechargeablelithium batteries.

Evaluation

1. For the five rechargeable lithium batteries obtained in each ofExamples 1 to 4 and Comparative Examples 1 to 4, evaluation wasconducted with respect to battery characteristics in the followingmanner.

Each rechargeable lithium battery is subjected to the following chargingand discharging cycle test using a charge-discharge system BT-2043(produced by Arbin Instruments). That is, a cycle in thatconstant-current charging is performed for 3 hours such a manner thatcharging is performed at a constant electric current of 1 A until thebattery voltage reaches 4.2 V and a given electric current is flown soas to maintain said voltage; a pause for 10 minutes is taken;discharging is performed until the battery voltage reaches 2.5 V at anelectric current of 1 A; and a pause for 10 minutes is taken, isrepeated many times, wherein the repeated cycle number of the chargingand discharging cycle when the battery suffers internal shorts (amongthe cathode and the anode) is examined.

The evaluated results are collectively shown in Table 4. Particularly,in Table 4, the repeated number of the charging and discharging cyclewhen the rechargeable lithium battery became suffered internal shorts ineach case is shown. The figure in Table 4 is a sum total of therechargeable lithium battery(s) suffered internal shorts after a certainrepeated cycle number of the charging and discharging cycle.

From the evaluated results, there were found the following facts. Thatis, all the five rechargeable lithium batteries obtained in each ofExamples 1 to 4 did not suffer internal shorts even when the chargingand discharging cycle was repeated 500 times. For the rechargeablelithium batteries obtained in Comparative Example 2, two of themsuffered internal shorts until 100th repetitive cycle, and all of themsuffered internal shorts until 200th repetitive cycle. The rechargeablelithium batteries obtained in Comparative examples 1 and 3 were not sodeteriorated as in the case of Comparative Example 2 but all of themsuffered internal shorts until 400th repetitive cycle. Theserechargeable lithium batteries were examined by decomposing them. As aresult, it was found that the separators or the solidified electrolytematerial layers as the ion conductors (or the isolators) were partiallydamaged in each case. The cause for this is considered such that theactive materials (the cathode active materials or/and the anode activematerials) were volume-expanded to apply a stress to the heat shieldingmember. TABLE 1 rechargeable number of rechargeable lithium battery inwhich lithium the anode and the cathode were internally shorted battery1^(st) 100^(th) 200^(th) 300^(th) 400^(th) 500^(th) obtained cycle cyclecycle cycle cycle cycle Example 1 0 0 0 0 0 0 Example 2 0 0 0 0 0 0Example 3 0 0 0 0 0 0 Example 4 0 0 0 0 0 0 Comparative 0 1 1 3 5 —Example 1 Comparative 0 2 5 — — — Example 2 Comparative 0 1 2 4 5 —Example 3

2. Each of the rechargeable lithium battery obtained in Example 1, thatobtained in Comparative Example 1, and that obtained in ComparativeExample 4 was evaluated in the following manner using aforesaidcharge-discharge system BT-2043.

For each rechargeable lithium battery, constant-current charging isperformed for 3 hours such a manner that charging is performed at aconstant electric current of 1 A until the battery voltage reaches 4.2 Vand a given electric current is flown so as to maintain said voltage.Thereafter, while measuring the battery voltage, the entire surface ofthe battery is pressed by means of an oil hydraulic press, wherein aload when the battery voltage is suddenly decreased is measured.

As a result, for the rechargeable lithium battery of Example 1, nosudden decrease in the battery voltage was occurred until a load of 49MPa. On the other hand, for the rechargeable lithium battery ofComparative Example 1, sudden decrease in the battery voltage wasoccurred at a load of 4.9 MPa, and for the rechargeable lithium batteryof Comparative Example 4, sudden decrease in the battery voltage wasoccurred already even at a load of 0.98 MPa.

From the evaluated results, the rechargeable lithium battery of thepresent invention was found to excel in withstand load.

EXAMPLE 5

The procedures of Example were repeated, except that the sealing member(b) was replaced by a rectangular plat sealing member with no concaveportion made of a stainless steel and which has a thickness of 0.15 mm,and a longitudinal length of 88 mm and a lateral length of 56 mm, andhas a peripheral collar portion with a width of 2 mm which iscorresponding to the collar portion (a-i) of the sealing member (a), toobtain six thin type rechargeable lithium batteries.

The five rechargeable lithium batteries were evaluated in the samemanner as that described in the foregoing evaluation 1. As a result, allthe rechargeable lithium batteries were not suffered internal shortseven when the charging and discharging cycle was repeated 500 times.

The remaining rechargeable lithium battery was evaluated in the samemanner as that described in the foregoing evaluation 2. As a result, nosudden decrease in the battery voltage was occurred until a load of 30MPa.

1-19. (canceled)
 20. A process for producing a rechargeable lithiumbattery, comprising the steps of: providing a battery main bodycomprising at least a cathode, an anode, and an ion conductor, a firstsealing member (a) having a concave portion with a peripheral portionsurrounding said concave portion and a peripheral collar portion (a-i)at said peripheral portion of said concave portion, and a second sealingmember (b) having a peripheral collar portion (b-i) at a region thereofwhich is corresponding to said peripheral portion of said first sealingmember (a); arranging said battery main body in said concave portion ofsaid first sealing member (a); mating said first sealing member (a) withsaid second sealing member (b) to oppose to each other such that theface of said concave portion of said first sealing member (a) is facedto said second sealing member (b) through said battery main body; andmutually welding said collar portion (a-i) of said first sealing member(a) and said collar portion (b-i) of said second sealing member (b). 21.The process according to claim 20, wherein as said second sealing member(b), there is used a sealing member having a concave portion with aperipheral portion surrounding said concave portion and a peripheralcollar portion at said peripheral portion of said concave portion. 22.The process according to claim 20 which includes a step of arranging apower output terminal comprising a cathode power output terminal and ananode power output terminal having an electrical continuity with saidbattery main body and an insulating portion for insulating said poweroutput terminal in said concave portion of said first sealing member(a).
 23. The process according to claim 20, wherein to mutually weldsaid peripheral collar portion (a-i) and said peripheral collar portion(b-i) is conducted by way of laser beam welding, electron beam welding,resistance welding, or ultrasonic welding.
 24. (canceled)
 25. Theprocess according to claim 22, wherein said insulating portion is formedto integrate with said cathode power output terminal and said anodepower output.